What is commonly used to increase the energy efficiency of windows?

Increasing the energy efficiency of windows is important for improving insulation, reducing heating and cooling costs, and enhancing overall comfort in buildings. Each of the options listed contributes to this goal in different ways.

Low-E coatings are specifically designed to reflect infrared light, keeping heat inside in winter and outside in summer. This effective insulation helps maintain a comfortable indoor temperature while reducing reliance on heating and air conditioning systems, leading to lower energy consumption.

Tinted glass reduces solar heat gain by filtering out certain wavelengths of light. This is particularly useful in warm climates or for buildings with large windows facing direct sunlight, as it helps keep interiors cooler and reduces the load on air conditioning systems.

Smart glass technology offers dynamic control of light and heat passing through windows. By changing its properties in response to environmental conditions (such as sunlight), smart glass can significantly enhance energy efficiency by optimizing the indoor climate throughout the day.

Since all these options play a role in enhancing the energy efficiency of windows, the most comprehensive choice is to include all of them. Each method has its benefits, and their combined use can lead to improved performance in windows, making option D the correct choice.